10 Key Parkinson's Disease Studies

April 28, 2009
Todd Kunkler

Here are 10 studies about Parkinson's disease which were among the hundreds cited by Susan H. Fox, MD, PhD, during her presentation on movement disorders at the 61st Annual Meeting of the American Academy of Neurology.

Among the hundreds cited by Susan H. Fox, MD, PhD, during her presentation on movement disorders at the 61st Annual Meeting of the American Academy of Neurology.

Update in the Epidemiology of Parkinson's Disease

Summary: “Epidemiologic studies have consistently found that some exposures are inversely (eg, cigarette smoking) or positively associated with Parkinson's disease (eg, pesticides), while their findings are, at the present time, less consistent for other exposures (eg, NSAIDs, vascular risk factors). Finally, recent studies have investigated new research fields (eg, hormonal factors, uric acid, pharmacoepidemiology) and additional data need to be collected.”

Efficacy of Risedronate against Hip Fracture in Patients with Neurological Diseases: A Meta-analysis of Randomized Controlled Trials

Summary: “The results of a meta-analysis of strictly conducted [randomized controlled trials] suggest that there is efficacy against hip fracture and safety with risedronate treatment in patients with neurological diseases including Alzheimer's disease, stroke, and Parkinson's disease.”

Test for LRRK2 Mutations in Patients with Parkinson’s Disease

Summary: “Neurologists should consider testing LRRK2 in Parkinson’s disease patients with affected first degree relatives where the onset is over the age of 40 years. A common G2019S mutation makes genetic testing straightforward and cost-effective. Age-related or reduced genetic penetrance means that LRRK2 mutations are also found in sporadic Parkinson’s disease patients; however, at present, there is little to support the widespread testing of these patients except in high-risk ethnic groups.”

'Rejuvenation' Protects Neurons in Mouse Models of Parkinson's Disease

Summary: “Why dopamine-containing neurons of the brain's substantia nigra pars compacta die in Parkinson's disease has been an enduring mystery. Our studies suggest that the unusual reliance of these neurons on L-type Cav1.3 Ca2+ channels to drive their maintained, rhythmic pacemaking renders them vulnerable to stressors thought to contribute to disease progression. The reliance on these channels increases with age, as juvenile dopamine-containing neurons in the substantia nigra pars compacta use pacemaking mechanisms common to neurons not affected in Parkinson's disease. These mechanisms remain latent in adulthood, and blocking Cav1.3 Ca2+ channels in adult neurons induces a reversion to the juvenile form of pacemaking. Such blocking ('rejuvenation') protects these neurons in both in vitro and in vivo models of Parkinson's disease, pointing to a new strategy that could slow or stop the progression of the disease.”

Fourteen-year Final Report of the Randomized PDRG-UK Trial Comparing Three Initial Treatments in PD

Summary: “Between 1985 and 1990, 782 patients were recruited into an open pragmatic multicenter trial and were randomized to l-dopa/decarboxylase inhibitor (DDCI), l-dopa/DDCI plus selegiline, or bromocriptine. The main endpoints were mortality, disability, and motor complications. For final follow-up, health-related quality of life and mental function were also assessed… Initial treatment with the dopamine agonist bromocriptine did not reduce mortality or motor disability and the initially reduced frequency in motor complications was not sustained. We found no evidence of a long-term benefit or clinically relevant disease-modifying effect with initial dopamine agonist treatment.”

Double-blind Trial of Levodopa/Carbidopa/Entacapone versus Levodopa/Carbidopa in Early Parkinson's Disease

Summary: “Four hundred twenty-three patients with early PD warranting levodopa were randomly assigned to treatment with LCE 100/25/200 or LC 100/25 three-times daily. The adjusted mean difference in total Unified Parkinson's disease Rating Scale (UPDRS) Parts II and III between groups using the analysis of covariance model (prespecified primary outcome measure) was 1.7 (standard error = 0.84) points favoring LCE (P = 0.045). Significantly greater improvement with LCE compared with LC was also observed in UPDRS Part II activities of daily living (ADL) scores (P = 0.025), Schwab and England ADL scores (blinded rater, P = 0.003; subject, P = 0.006) and subject-reported Clinical Global Impression (CGI) scores (P = 0.047). There was no significant difference in UPDRS Part III or investigator-rated CGI scores. Wearing-off was observed in 29 (13.9%) subjects in the LCE group and 43 (20.0%) in the LC group (P = 0.099). Dyskinesia was observed in 11 (5.3%) subjects in the LCE group and 16 (7.4%) in the LC group (P = 0.367). Nausea and diarrhea were reported more frequently in the LCE group. LCE provided greater symptomatic benefit than LC and did not increase motor complications.”

Movement Disorder Society-sponsored Revision of the Unified Parkinson's Disease Rating Scale (MDS-UPDRS): Scale Presentation and Clinimetric Testing Results

Summary: “Movement disorder specialists and study coordinators administered the UPDRS (55 items) and MDS-UPDRS (65 items) to 877 English speaking (78% non-Latino Caucasian) patients with Parkinson's disease from 39 sites. We compared the two scales using correlative techniques and factor analysis. The MDS-UPDRS showed high internal consistency (Cronbach's alpha = 0.79-0.93 across parts) and correlated with the original UPDRS (P = 0.96). MDS-UPDRS across-part correlations ranged from 0.22 to 0.66. Reliable factor structures for each part were obtained (comparative fit index > 0.90 for each part), which support the use of sum scores for each part in preference to a total score of all parts. The combined clinimetric results of this study support the validity of the MDS-UPDRS for rating PD.”

The Unified Dyskinesia Rating Scale: Presentation and Clinimetric Profile

Summary: “We developed and tested a rating scale aimed to capture the essential features of dyskinesia in Parkinson's disease (PD). Although several scales assess selected attributes of PD-dyskinesias, no comprehensive rating tool exists. Available rating scales were evaluated by the investigators and patient focus groups. Modifications were finalized into the Unified Dyskinesia Rating Scale (UDysRS). The UDysRS has four parts: I: Historical Disability (patient perceptions) of On-Dyskinesia impact (maximum 44 points); II: Historical Disability (patient perceptions) of Off-Dystonia impact (maximum 16 points); III: Objective Impairment (dyskinesia severity, anatomical distribution over seven body regions, and type (choreic or dystonic) based on four activities observed or video-recorded (28 points); IV: Objective Disability based on Part III activities (maximum 16 points). For clinimetric testing, 70 PD patients with all severities of dyskinesia were interviewed and videotaped. Twenty movement disorder experts rated the videotapes with the UDysRS. Internal consistency was examined with Cronbach's alpha. Inter- and intra-rater reliability was evaluated with generalized weighted and nonweighted Kappa coefficients, and intraclass correlation coefficients. Both subjective (Sections I and II) and objective (Sections III and IV) demonstrated high internal consistency (alpha: 0.915, 0.971). Interrater reliability for the objective sections was acceptable for all items and likewise for intrarater reliability except for right leg. Reliable factor structures were found for both subjective (six factors) and objective sections (five factors). The UDysRS is a clinimetrically sound rating scale for dyskinesia in PD, demonstrating acceptable levels of internal consistency and inter- and intra-rater reliability.”

Rotigotine Transdermal Patch in Early Parkinson's Disease: A Randomized, Double-blind, Controlled Study versus Placebo and Copinirole

Summary: “The responder rate in the rotigotine group was significantly higher than in the placebo group (52% vs. 30%, P < 0.0001). Transdermal rotigotine at doses ≤8 mg/24 h did not show noninferiority to ropinirole at doses ≤24 mg/day. In a post-hoc subgroup analysis, rotigotine ≤8 mg/24 hours had a similar efficacy to ropinirole at doses ≤12 mg/day. The rotigotine transdermal patch was well tolerated. The most common adverse events were application-site reactions, nausea, and somnolence. Application-site reactions were predominantly mild or moderate in intensity. In conclusion, the rotigotine transdermal patch represents an effective and safe option for the treatment of patients with early Parkinson's disease.”

Hippocampal Head Atrophy Predominance in Parkinson’s Disease with Hallucinations and with Dementia

Summary: “We studied regional gray matter density in the hippocampus in Parkinson’s disease (PD) patients. We obtained magnetic resonance scans in 44 PD patients (PD patients with dementia (PDD) = 9, non-demented PD patients with visual hallucinations (PD + VH) = 16, and PD patients without dementia and without visual hallucinations (PD - VH) = 19) and 56 controls matched for age and years of education. A region of interest (ROI) of the hippocampus following voxel-based morphometry (VBM) procedures was used to perform group comparisons, single-case individual analysis and correlations with learning scores. Group comparisons showed that PDD patients and PD+VH patients had significant hippocampal gray matter loss compared to controls. In PDD patients, hippocampal gray matter loss involved the entire hippocampus and in PD+VH this reduction was mainly confined to the hippocampal head. 78 % of PDD patients, 31 % of PD+VH patients and 26 % of PD-VH patients had hippocampal head gray matter loss when compared to controls. These results suggest that in PD the neurodegenerative process in the hippocampus starts in the head of this structure and later spreads to the tail and that, in addition, memory impairment assessed by Rey’s Auditory Verbal Learning Test (RAVLT) correlates with hippocampal head gray matter loss.”